Wound dovetail wedge for marine propeller retention

ABSTRACT

A marine propeller composite blade an axially extending composite blade root including a dovetail wound in a partial spiral or helix around a centerline. Dovetail tapering down in width between clockwise and counter-clockwise dovetail sides of dovetail from dovetail bottom in a radially outwardly direction away from centerline. Marine propeller may include composite blade roots mounted in axially extending hub slots in a metallic hub, axially extending wedges disposed within the hub slots circumferentially between the blade roots and one of clockwise slot sides and counter-clockwise slot sides, and the wedges abutting the blade roots and the one of clockwise slot sides and counter-clockwise slot sides. Wedges and hub slots wound in a partial spiral or helix around a centerline. Radial retention means for radially retaining wedges in hub slots may include bolts engaging wedges and screwed into threaded holes in hub.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates generally to marine propellers and, specifically, relates to a metallic hub and blade assembly with composite blades.

Background Information

Marine propellers have traditionally been cast or forged of metal and the hub and blades were formed as a single unitary part. This design provided strength and reliability that the blades would not come loose from the hub. Disadvantages include that if the blade struck a foreign object, enormous forces could be transmitted through the metal blade and hub to the drive shaft, possibly bending it or damaging its mounting. Also the blades are heavy. Damage to even one blade required replacement of the entire assembly because the blades and hub formed a single piece.

Molded plastic propellers were developed. U.S. Pat. No. 4,930,987 discloses marine propeller blades including, at their roots, a root portion that slides axially into a re-entrant cavity that extends axially in the hub. End caps prevent axial removal of the blade roots from the hub. This makes it possible to replace an individual damaged blade, and the hubs are interchangeable from ship to ship, although the blades may vary slightly. All of the parts are injection molded of a high-strength fiber-reinforced plastic.

It is desirable to provide marine propeller assemblies with light-weight blades securely attached to metallic hubs.

BRIEF DESCRIPTION OF THE INVENTION

A marine propeller blade includes a composite propeller blade with an axially extending composite blade root with a dovetail wound in a partial spiral or helix around a centerline. The dovetail tapers down in width between clockwise and counter-clockwise dovetail sides of the dovetail from a dovetail bottom in a radially outwardly direction away from the centerline. The composite propeller blade may include a blade suction or forward side and a pressure or aft side extending from the blade root to a blade tip.

A marine propeller includes a metallic hub and blade assembly with composite blades having axially extending composite blade roots mounted in axially extending hub slots in a metallic hub. Axially extending wedges are disposed within the hub slots circumferentially between the blade roots and one of clockwise slot sides and counter-clockwise slot sides and the wedges abut the blade roots and one of the clockwise slot sides and counter-clockwise slot sides. A radial retention means may be used for radially retaining and securing the wedges in the hub slots such as bolts engaging the wedges and screwed into threaded holes in the hub at a slot bottom of the hub slot.

Each blade root may include a dovetail wound in a partial spiral or helix around the centerline and the dovetail tapers down in width between circumferentially spaced apart clockwise and counter-clockwise dovetail sides of the dovetail in a radially outwardly direction away from the centerline.

Each wedge may taper down in width between clockwise and counter-clockwise wedge sides in a radially inwardly direction from a wedge outer surface towards the axis or centerline of the hub and the dovetails and the wedges may be wound in partial spirals or helixes around the centerline. A first one of the clockwise and counter-clockwise wedge sides may abut and be flush and conformal with a first one of the counter-clockwise dovetail sides respectively, a second one of the clockwise and counter-clockwise wedge sides may abut and be flush and conformal with a second one of the counter-clockwise dovetail sides respectively, an obtuse dovetail angle may extend between a second one of counter-clockwise slot sides and a slot bottom of the hub slot, and an acute dovetail angle may extend between a first one of the counter-clockwise slot sides and the slot bottom of the hub slot. The hub slots being wound in partial spirals or helixes around the centerline.

Each composite propeller blade may include a blade suction or forward side and a pressure or aft side and a blade tip representing a maximum reach of the composite propeller blade from the centerline and separating leading and trailing edges of the blade.

A marine propeller metallic hub may include hub slots axially extending through a metallic hub for receiving blade roots of blades and the hub slots being wound in partial spirals or helixes around a centerline of the hub. The hub slots may include circumferentially spaced apart counter-clockwise slot sides and a slot bottom therebetween, an obtuse dovetail angle extending between a second one of the counter-clockwise slot sides and the slot bottom, and an acute dovetail angle extending between a first one of the counter-clockwise slot sides and the slot bottom. The metallic hub being conical or cylindrical.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, in accordance with preferred and exemplary embodiments, together with further objects and advantages thereof, is described in the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a forward looking aft perspective view illustration of an exemplary embodiment of a marine propeller assembly with a composite blade mounted to a metallic hub by a spiral dovetail root of the blade secured in a spiral dovetail slot in the hub and secured by a spiral wedge in the slot.

FIG. 2 is a forward looking aft perspective schematical view illustration of a single one of the blades and the wedges mounted in the metallic hub illustrated in FIG. 1.

FIG. 3 is a longitudinal cross-sectional view illustration of the blade and wedge mounted in the metallic hub illustrated in FIG. 2.

FIG. 4 is an exploded view of the blade and wedge mounted in the metallic hub illustrated in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Illustrated schematically in FIG. 1 is a marine propeller 10 including a metallic hub and blade assembly 12. The exemplary embodiment of the assembly 12 illustrated herein has composite blades 14 with axially extending composite blade roots 18 mounted in axially extending hub slots 20 in a metallic hub 28 and secured therein with axially extending wedges 22. The exemplary embodiment of the blade root 18 includes a dovetail 26 which is secured in a hub slot 20 in the hub 28 by a radially inserted and secured dovetail wedge 22.

Referring to FIGS. 1 and 2, each of the composite blades 14 includes a blade back or suction or forward side 15 of the blade 14 (surface facing the bow) extending from the blade root 18 out to a blade tip 29. A blade face is referred to as a pressure, pitch, or aft side 16 of the blade 14 (surface facing the stern). The blade root 18 include a fillet 17 which is a region of transition from the blade surfaces, the forward and aft sides 15 and 16, and blade edge 19 to a hub periphery 21 where the blade 14 attaches to the hub 28. The blade tip 29 represents a maximum reach of the blade 14 from the axis or centerline 48 of the hub 28 and separates leading and trailing edges LE, TE of the blade.

Referring to FIGS. 2-4, the dovetail 26 is characterized by circumferentially spaced apart axially extending clockwise and counter-clockwise dovetail sides 30, 32. The dovetail 26 includes a dovetail bottom 36 from which the clockwise and counter-clockwise dovetail sides 30, 32 are angled so that the dovetail 26 tapers down in width W between the clockwise and counter-clockwise dovetail sides 30, 32 in a radially outwardly direction away from an axis or centerline 48 of the hub 28. The dovetails 26, wedges 22, and hub slots 20 are wound in spirals or helixes around the centerline 48. The winding is done to accommodate the curvature and added length of the root. This allows a long axial blade to be attached to a low radius hub.

Referring to FIGS. 2 and 3, the hub 28 is a body of revolution circumscribed about the axis or centerline 48 of the hub 28. A hub outer surface 40 of the hub 28 is illustrated herein as being conical and tapering down in diameter D from an upstream or forward end 42 to a downstream or aft end 44. The blade roots 18, hub slots 20, and wedges 22 wind around the centerline 48 in spirals less than 1 full turn which is 360 degrees and extend axially from the upstream or forward end 42 to the downstream or aft end 44. The wedges 22 are radially inserted into the hub slots 20 after the dovetails 26 of the blade roots 18 are inserted. The wedges 22 are radially retained and secured in the hub slots 20 by radial retention means such as bolts 24 engaging the wedges 22 and screwed into threaded holes 25 in the hub 28 at a slot bottom 38 of the hub slot 20.

The dovetail 26 has a radially inner or dovetail bottom 36 which is complimentary and conformal with the slot bottom 38 of the hub slot 20. An acute dovetail angle 54 extends between one side of the hub slot 20, illustrated herein as clockwise slot side 50 and the slot bottom 38 of the hub slot 20. The same angle extends between the clockwise dovetail side 30 and the dovetail bottom 36 of the dovetail 26. This helps radially retain the dovetail 26 of the blade root 18 in the hub slot 20. The dovetail 26 illustrated herein includes the same acute dovetail angle 54 between the clockwise and counter-clockwise dovetail sides 30, 32 and the dovetail bottom 36 of the dovetail 26.

The wedge 22 is characterized by slanted circumferentially spaced apart axially extending clockwise and counter-clockwise wedge sides 60, 62. The wedge 22 includes a wedge outer surface 58 from which the wedge 22 tapers down in width W between the clockwise and counter-clockwise wedge sides 60, 62 in a radially inwardly direction towards the axis or centerline 48 of the hub 28. A first wedge side, illustrated herein as the clockwise wedge side 60, abuts and is flush and conformal with the counter-clockwise side 32 of the dovetail 26. An obtuse dovetail angle 56 extends between a counter-clockwise slot side 52 and the slot bottom 38 of the hub slot 20. A second wedge side, illustrated herein as the counter-clockwise wedge side 62, abuts and is flush and conformal with the counter-clockwise slot side 52 of the dovetail 26.

The hub 28 and the hub outer surface 40 of the hub 28 may be cylindrical. In such a case, the hub outer surface 40 would have a constant diameter D from the upstream or forward end 42 to the downstream or aft end 44. The blade roots 18, hub slots 20, and wedges 22 would wind around the centerline 48 in helixes less than 1 full turn which is 360 degrees and extend axially from the upstream or forward end 42 to the downstream or aft end 44.

While there have been described herein what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein and, it is therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention. Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims. 

What is claimed:
 1. A marine propeller blade comprising: a composite propeller blade with an axially extending composite blade root, and the blade root including a dovetail wound in a partial spiral or helix around a centerline.
 2. The marine propeller blade as claimed in claim 1 further comprising the dovetail tapering down in width between clockwise and counter-clockwise dovetail sides of the dovetail from a dovetail bottom in a radially outwardly direction away from the centerline.
 3. The marine propeller blade as claimed in claim 2 further comprising the composite propeller blade including a blade suction or forward side and a pressure or aft side extending from the blade root to a blade tip.
 4. The marine propeller blade as claimed in claim 3 further comprising the blade tip representing a maximum reach of the composite propeller blade from the centerline and separating leading and trailing edges of the blade.
 5. A marine propeller comprising: a metallic hub and blade assembly including composite blades with axially extending composite blade roots mounted in axially extending hub slots in a metallic hub, axially extending wedges disposed within the hub slots circumferentially between the blade roots and one of clockwise slot sides and counter-clockwise slot sides, and the wedges abutting the blade roots and the one of clockwise slot sides and counter-clockwise slot sides.
 6. The marine propeller as claimed in claim 5 further comprising a radial retention means for radially retaining and securing the wedges in the hub slots.
 7. The marine propeller as claimed in claim 6 further comprising the radial retention means including bolts engaging the wedges and screwed into threaded holes in the hub at a slot bottom of the hub slot.
 8. The marine propeller as claimed in claim 5 further comprising each blade root including a dovetail wound in a partial spiral or helix around the centerline and the dovetail tapering down in width between circumferentially spaced apart clockwise and counter-clockwise dovetail sides of the dovetail in a radially outwardly direction away from the centerline.
 9. The marine propeller as claimed in claim 8 further comprising a radial retention means for radially retaining and securing the wedges in the hub slots.
 10. The marine propeller as claimed in claim 9 further comprising the radial retention means including bolts engaging the wedges and screwed into threaded holes in the hub at a slot bottom of the hub slot.
 11. The marine propeller as claimed in claim 10 further comprising each composite propeller blade including a blade suction or forward side and a pressure or aft side and a blade tip representing a maximum reach of the composite propeller blade from the centerline and separating leading and trailing edges of the blade.
 12. The marine propeller as claimed in claim 5 further comprising: each blade root including a dovetail tapering down in width between circumferentially spaced apart clockwise and counter-clockwise dovetail sides of the dovetail from a dovetail bottom in a radially outwardly direction away from the centerline, each wedge tapering down in width between clockwise and counter-clockwise wedge sides in a radially inwardly direction from a wedge outer surface towards the axis or centerline of the hub, and the dovetails and the wedges wound in partial spirals or helixes around the centerline.
 13. The marine propeller as claimed in claim 12 further comprising: a first one of the clockwise and counter-clockwise wedge sides abutting and flush and conformal with a first one of the counter-clockwise dovetail sides respectively, a second one of the clockwise and counter-clockwise wedge sides abutting and flush and conformal with a second one of the counter-clockwise dovetail sides respectively, an obtuse dovetail angle extending between a second one of counter-clockwise slot sides and a slot bottom of the hub slot, and an acute dovetail angle extending between a first one of the counter-clockwise slot sides and the slot bottom of the hub slot.
 14. The marine propeller as claimed in claim 13 further comprising the hub slots wound in partial spirals or helixes around the centerline.
 15. The marine propeller as claimed in claim 14 further comprising a radial retention means for radially retaining and securing the wedges in the hub slots.
 16. The marine propeller as claimed in claim 15 further comprising the radial retention means including bolts engaging the wedges and screwed into threaded holes in the hub at a slot bottom of the hub slot.
 17. The marine propeller as claimed in claim 16 further comprising each composite propeller blade including a blade suction or forward side and a pressure or aft side and a blade tip representing a maximum reach of the composite propeller blade from the centerline and separating leading and trailing edges of the blade.
 18. A marine propeller metallic hub comprising hub slots axially extending through a metallic hub for receiving blade roots of blades and the hub slots wound in partial spirals or helixes around a centerline of the hub.
 19. The marine propeller as claimed in claim 18 further comprising: the hub slots including circumferentially spaced apart counter-clockwise slot sides and a slot bottom therebetween, an obtuse dovetail angle extending between a second one of the counter-clockwise slot sides and the slot bottom, and an acute dovetail angle extending between a first one of the counter-clockwise slot sides and the slot bottom.
 20. The marine propeller as claimed in claim 19 further comprising the metallic hub being conical or cylindrical. 